Double- headed piston type swash plate compressor

ABSTRACT

A double-headed piston type swash plate compressor includes a rotation shaft, a housing, a swash plate, two cylinder bores, a double-headed piston, and two shoes. The double-headed piston includes two shoe holders, a neck, two heads, and two coupling portions. At least one of the two coupling portions includes a load receiving portion. The load receiving portion is configured to receive bending load that is applied from the swash plate to the double-headed piston and acts toward an inner side in the radial direction. The load receiving portion is separated from the wall surface of the cylinder bore when load applied to the double-headed piston is less than a specific threshold value. The load receiving portion abuts against the inner wall of the cylinder bore and receives the bending load when the load applied to the double-headed piston is greater than the specific threshold value.

BACKGROUND OF THE INVENTION

The present invention relates to a double-headed piston type swash platecompressor.

One example of a compressor is a double-headed piston type swash platecompressor including a swash plate that rotates when a rotation shaftrotates and a double-headed piston that reciprocates in a pair ofcylinder bores when the swash plate rotates. The double-headed pistoncompresses fluid in compression chambers that are defined in the twocylinder bores when the double-headed piston reciprocates (refer toJapanese Laid-Open Patent Publication No. 2015-161173). Thedouble-headed piston type swash plate compressor compresses fluid thatis subject to compression when the double-headed piston reciprocates.

In the structure of the double-headed piston type swash platecompressor, the fluid, which is subject to compression, and the swashplate apply load to the double-headed piston. Load includes bending loadthat acts toward the inner side in the radial direction of the rotationshaft. Thus, the double-headed piston requires strength that countersthe bending load. Abutment of the double-headed piston against an innerwall of the cylinder bore may be increased to increase the strength ofthe piston. However, this will increase power loss and is not desirable.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a double-headedpiston type swash plate compressor that receives bending load applied toa double-headed piston.

To achieve the above object, a double-headed piston type swash platecompressor according to one aspect of the present invention includes arotation shaft, a housing, a swash plate, two cylinder bores, adouble-headed piston, and two shoes. The rotation shaft extends in anaxial direction and a radial direction. The housing accommodates therotation shaft. The swash plate rotates when the rotation shaft rotates.The two cylinder bores are located in the housing at an outer side ofthe rotation shaft in the radial direction. The double-headed pistonreciprocates in the two cylinder bores. The two shoes couple thedouble-headed piston to the swash plate. The two cylinder bores and thedouble-headed piston define two compression chambers. Rotation of theswash plate reciprocates the double-headed piston in the two cylinderbores and compresses fluid in each of the compression chambers. Thedouble-headed piston includes two shoe holders, a neck, two heads, andtwo coupling portions. The two shoe holders hold the two shoes. The twoshoe holders are opposed to each other in an axial direction of thedouble-headed piston. The neck couples the two shoe holders. The neck islocated at an outer circumferential side of the swash plate anddeformable in the radial direction. The two heads are respectivelylocated at two ends of the double-headed piston in the axial directionof the double-headed piston. Each of the two heads includes a sidesurface opposing a wall surface of the cylinder bore. Two couplingportions couple the two shoe holders and the two heads, respectively. Atleast one of the two coupling portions includes a load receiving portionlocated between the corresponding head and the corresponding shoe holderas viewed in the radial direction. The load receiving portion isconfigured to receive bending load that is applied from the swash plateto the double-headed piston and acts toward an inner side in the radialdirection. The load receiving portion is separated from the wall surfaceof the cylinder bore when load applied to the double-headed piston isless than a specific threshold value. The load receiving portion abutsagainst the inner wall of the cylinder bore and receives the bendingload when the load applied to the double-headed piston is greater thanthe specific threshold value.

Other aspects and advantages of the present invention will becomeapparent from the following description, taken in conjunction with theaccompanying drawings, illustrating by way of example the principles ofthe invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention, together with objects and advantages thereof, may best beunderstood by reference to the following description of the presentlypreferred embodiments together with the accompanying drawings in which:

FIG. 1 is a cross-sectional view schematically showing a double-headedpiston type swash plate compressor;

FIG. 2 is a perspective view of a double-headed piston shown in FIG. 1;

FIG. 3 is a perspective view of the double-headed piston shown in FIG.1;

FIG. 4 is a plan view of the double-headed piston shown in FIG. 1 asviewed from a radially inner side;

FIG. 5 is an enlarged view schematically showing the double-headedpiston shown in FIG. 1 and the surrounding of the double-headed pistonduring a low-load period;

FIG. 6 is an enlarged view schematically showing the double-headedpiston shown in FIG. 1 and the surrounding of the double-headed pistonduring a high-load period; and

FIG. 7 is an enlarged view schematically showing the double-headedpiston shown in FIG. 1 and the surrounding of the double-headed pistonduring the high-load period.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

One embodiment of the present invention will now be described withreference to FIGS. 1 to 7. The double-headed piston type swash platecompressor of the present embodiment is installed in a vehicle for usewith a vehicle air conditioner. That is, fluid that is subject tocompression by the double-headed piston type swash plate compressor ofthe present embodiment is refrigerant containing oil (lubricant). InFIGS. 1 and 5 to 7, the double-headed piston 100 is shown in a sideview. In FIG. 5, the double-headed piston 100 is shown in a side viewand a partially enlarged view.

As shown in FIG. 1, a double-headed piston type swash plate compressor10 (hereinafter referred to as compressor 10) includes a housing 11 thatforms the shell of the compressor 10. The entire housing 11 is tubular.

The housing 11 rotationally accommodates a rotation shaft 20. Therotation shaft 20 is located near the center in the housing 11. Theaxial direction Z of the rotation shaft 20 corresponds to the axialdirection of the housing 11. In the following description, the axialdirection Z of the rotation shaft 20 is referred to as the axialdirection Z.

The housing 11 includes a tubular front housing 12, which forms one endof the housing 11 in the axial direction Z, a tubular rear housing 13,which has a bottom and forms the other end of the housing 11 in theaxial direction Z, and two cylinder blocks 14 and 15 (first cylinderblock 14 and second cylinder block 15), which are arranged between thefront housing 12 and the rear housing 13. The cylinder blocks 14 and 15are cylindrical and respectively include first and second shaft holes 21and 22 through which the rotation shaft 20 can be inserted.

The first cylinder block 14 includes the first shaft hole 21 thatextends through the first cylinder block 14 in the axial direction Z.The first shaft hole 21 includes a first small diameter hole 21 a, whichhas a slightly larger diameter than the rotation shaft 20, and a firstlarge diameter hole 21 b, which is larger than the first small diameterhole 21 a. The first small diameter hole 21 a is located closer to thefront housing 12 than the first large diameter hole 21 b.

The second cylinder block 15 includes the second shaft hole 22 thatextends through the second cylinder block 15 in the axial direction Z.The second shaft hole 22 includes a second small diameter hole 22 a,which has a slightly larger diameter than the rotation shaft 20, and asecond large diameter hole 22 b, which is larger than the second smalldiameter hole 22 a. The second small diameter hole 22 a is locatedcloser to the rear housing 13 than the second large diameter hole 22 b.The two cylinder blocks 14 and 15 are coupled to each other with the twoshaft holes 21 and 22 (more specifically, two large diameter holes 21 band 22 b) opposing each other in the axial direction Z.

A first valve/port body 23 is arranged between the front housing 12 andthe first cylinder block 14. A second valve/port body 24 is arrangedbetween the rear housing 13 and the second cylinder block 15. Thevalve/port bodies 23 and 24 each have the form of a flat ring. Thevalve/port bodies 23 and 24 have a larger inner diameter than therotation shaft 20.

The rotation shaft 20 is inserted through the two shaft holes 21 and 22and the two valve/port bodies 23 and 24 and extended from the fronthousing 12 to the rear housing 13. In this case, one end of the rotationshaft 20 in the axial direction Z is located in the front housing 12,and the other end of the rotation shaft 20 in the axial direction Z islocated in a regulation chamber A1, which is defined by the rear housing13 and the second cylinder block 15. That is, the rotation shaft 20extends through the two cylinder blocks 14 and 15. The regulationchamber A1 will be described later.

As shown in FIG. 1, a first radial bearing 31 that rotationally supportsthe rotation shaft 20 is arranged between the rotation shaft 20 and awall surface of the first small diameter hole 21 a. In the same manner,a second radial bearing 41 that rotationally supports the rotation shaft20 is arranged between the rotation shaft 20 and a wall surface of thesecond small diameter hole 22 a. The rotation shaft 20 is supported bythe two radial bearings 31 and 41 in the housing 11 in a rotatablemanner.

The rotation shaft 20 includes a first shaft projection 20 a and asecond shaft projection 20 b. The first shaft projection 20 a is locatedin the first large diameter hole 21 b and projected in the radialdirection R of the rotation shaft 20 (hereinafter referred to as theradial direction R), and the second shaft projection 20 b is located inthe second large diameter hole 22 b and projected in the radialdirection R. The first shaft projection 20 a is opposed to a ring-shapedstep surface in the axial direction X. The step surface connects thefirst small diameter hole 21 a to the first large diameter hole 21 b. Afirst thrust bearing 32 is arranged between the first shaft projection20 a and the step surface. The second shaft projection 20 b is opposedto a ring-shaped step surface in the axial direction X. The step surfaceconnects the second small diameter hole 22 a to the second largediameter hole 22 b. A second thrust bearing 42 is arranged between thesecond shaft projection 20 b and the step surface.

The housing 11 includes two suction chambers 33 and 43 (first suctionchamber 33 and second suction chamber 43) and two discharge chambers 34and 44 (first discharge chamber 34 and second discharge chamber 44).Each of the first suction chamber 33 and the first discharge chamber 34is defined by the front housing 12 and the first valve/port body 23.Each of the second suction chamber 43 and the second discharge chamber44 is defined by the rear housing 13 and the second valve/port body 24.The two suction chambers 33 and 43 oppose each other in the axialdirection Z, and the two discharge chambers 34 and 44 oppose each otherin the axial direction Z. The suction chambers 33 and 43 and thedischarge chambers 34 and 44 are formed to be annular as viewed in theaxial direction Z, and the discharge chambers 34 and 44 are located atthe outer sides of the suction chambers 33 and 43.

As shown in FIG. 1, the compressor 10 includes a swash plate 50 thatrotates when the rotation shaft 20 rotates. The swash plate 50 isinclined with respect to a direction that is orthogonal to the axialdirection Z of the rotation shaft 20.

The swash plate 50 includes a swash plate body 52, which has the form ofa flat ring. The swash plate body 52 includes a swash plate insertionhole 51 through which the rotation shaft 20 is inserted. The swash platebody 52 includes a first inclined surface 52 a, which is directed towardthe first cylinder block 14, and a second inclined surface 52 b, whichis directed toward the side opposite to the first inclined surface 52 a.

The swash plate 50 of the present embodiment is configured so that theinclination angle can be changed with respect to the directionorthogonal to the axial direction Z of the rotation shaft 20.

The housing 11 includes a swash plate chamber A2 that accommodates theswash plate 50. The swash plate chamber A2 is defined by the twocylinder blocks 14 and 15. The swash plate chamber A2 is located betweenthe two shaft holes 21 and 22 and is in communication with the two shaftholes 21 and 22.

As shown in FIG. 1, a side wall of the second cylinder block 15 definingthe swash plate chamber A2 includes a suction port 53. Thus, the suctionport 53 is in communication with the swash plate chamber A2. Further,the housing 11 includes a suction passage 54 through which the swashplate chamber A2 is in communication with the suction chambers 33 and43. The suction passage 54 includes a first suction passage 54 a and asecond suction passage 54 b. The first suction passage 54 a extendsthrough the first cylinder block 14 and the first valve/port body 23 inthe axial direction Z and allows communication between the swash platechamber A2 and the first suction chamber 33. The second suction passage54 b extends through the second cylinder block 15 and the secondvalve/port body 24 in the axial direction Z and allows communicationbetween the swash plate chamber A2 and the second suction chamber 43. Aplurality of the suction passages 54 a and 54 b extend in thecircumferential direction around the shaft holes 21 and 22 in thecylinder blocks 14 and 15.

In such a structure, fluid that is drawn from the suction port 53 flowsthrough the swash plate chamber A2 and the suction passage 54 into thesuction chambers 33 and 43. In this case, the swash plate chamber A2 andthe two large diameter holes 21 b and 22 b that are in communicationwith the swash plate chamber A2 have the same pressure as the fluiddrawn from the suction port 53.

The housing 11 includes a discharge passage 55 that is in communicationwith the two discharge chambers 34 and 44. The discharge passage 55 islocated at the outer side of the swash plate chamber A2 and cylinderbores 91 and 92 (first and second cylinder bores 91 and 92, describedbelow) in the radial direction R. The discharge passage 55 is incommunication with a discharge port 56, which is located in the housing11 (more specifically, side wall of second cylinder block 15). Fluid inthe two discharge chambers 34 and 44 is discharged out of the dischargeport 56 through the discharge passage 55.

As shown in FIG. 1, the compressor 10 includes a link mechanism 60 thatallows the inclination angle of the swash plate 50 to change and linksthe swash plate 50 to the rotation shaft 20 so that the swash plate 50and the rotation shaft 20 integrally rotate. The link mechanism 60 islocated closer to the front housing 12 than the swash plate 50 exceptfor part of the link mechanism 60.

The link mechanism 60 includes a lug arm 61, a first link pin 62, and asecond link pin 63. The lug arm 61 extends from the first large diameterhole 21 b to the swash plate chamber A2. The first link pin 62 pivotallycouples the lug arm 61 to the swash plate 50. The second link pin 63pivotally couples the lug arm 61 to the rotation shaft 20.

The lug arm 61 is L-shaped and includes a basal portion opposing thefront housing 12 and a distal portion opposing the swash plate 50. Thedistal portion of the lug arm 61 projects out of the swash plate 50toward the rear housing 13 through an arm through hole 52 c in the swashplate body 52 of the swash plate 50. The projecting portion includes aweight.

The arm through hole 52 c, for example, does not have an annular shapeextending over the entire circumference of the swash plate 50 and isrectangular as viewed in the axial direction Z. The arm through hole 52c includes an inner surface including two opposing inner surfaces thatare opposed to each other in the direction orthogonal to both of thethickness-wise direction of the swash plate 50 and the directionparallel to the axes of the swash plate insertion hole 51 and the armthrough hole 52 c.

The first link pin 62 is, for example, cylindrical. The first link pin62 is located in the arm through hole 52 c so that the axial directionof the first link pin 62 corresponds to the opposing direction of thetwo opposing inner surfaces. The first link pin 62 is extended through aportion of the lug arm 61 extending in the axial direction Z andattached to the swash plate 50. The portion of the lug arm 61 extendingin the axial direction Z is supported by the swash plate 50 pivotallyabout the axis of the first link pin 62, which serves as the first pivotcenter M1.

The second link pin 63 is, for example, cylindrical. The second link pin63 is arranged so that the axial direction of the second link pin 63 isparallel to the axial direction of the first link pin 62. The secondlink pin 63 is located in the basal portion of the lug arm 61 separatedfrom where the lug arm 61 extends in the axial direction Z. The secondlink pin 63 is extended through the basal portion of the lug arm 61 andfixed to the rotation shaft 20. The basal portion of the lug arm 61 ispivotally supported by the rotation shaft 20 about the axis of thesecond link pin 63, which serves as the second pivot center M2.

As shown in FIG. 1, the compressor 10 includes an actuator 70 thatchanges the inclination angle of the swash plate 50. The actuator 70 islocated closer to the rear housing 13 than the swash plate 50.

The actuator 70 includes a movable body 71 that is movable in the axialdirection Z, and a partition 72 that defines a control chamber A3 incooperation with the movable body 71, and two coupling pieces 73 thatcouple the movable body 71 to the swash plate 50. The compressionchamber A3 is used to control the inclination angle of the swash plate50.

The movable body 71 has the form of a tube (more specifically,cylindrical tube) and includes a bottom and a tubular portion. Themovable body opens toward one side. The bottom of the movable body 71includes an insertion hole through which the rotation shaft 20 can beinserted. The movable body 71 rotates integrally with the rotation shaft20 with the rotation shaft 20 inserted through the insertion hole andthe open end of the movable body 71 directed toward the swash platechamber A2.

The partition 72 has the form of a flat ring and has an outer diameterthat is set to be substantially the same as an inner diameter of themovable body 71. The partition 72, which is fitted onto the rotationshaft 20 and into the movable body 71, is fixed to the rotation shaft 20so that the partition 72 rotates integrally with the rotation shaft 20.The partition 72 closes the open end of the movable body 71 that isclose to the swash plate chamber A2. The control chamber A3 is definedby an inner circumferential surface of the movable body 71 and a surfaceof the partition 72 located at the side opposite to the swash platechamber A2.

A portion between the inner circumferential surface of the movable body71 and an outer circumferential surface of the partition 72 is sealed torestrict movement of fluid between the control chamber A3 and the swashplate chamber A2. This allows the control chamber A3, the swash platechamber A2, and the second large diameter hole 22 b to have differentpressures. The position of the movable body 71 changes in accordancewith the pressure difference of the control chamber A3 and the swashplate chamber A2.

The rotation shaft 20 includes a shaft passage 74 that allowscommunication between the regulation chamber A1 and the control chamberA3. The shaft passage 74 includes an axial portion, which opens in theregulation chamber A1 and extends in the axial direction Z, and a radialportion, which is in communication with the axial portion. The radialportion opens in the control chamber A3 and extends in the radialdirection R. The shaft passage 74 allows fluid to move between thecontrol chamber A3 and the regulation chamber A1. Thus, the controlchamber A3 and the regulation chamber A1 have the same pressure.

The compressor 10 includes a pressure controller 75 that controls thepressure of the regulation chamber A1. The pressure controller 75includes a low-pressure passage that allows communication between thesecond suction chamber 43 and the regulation chamber A1, a high-pressurepassage that allows communication between the second discharge chamber44 and the regulation chamber A1, a valve that is located on thelow-pressure passage and regulates the amount of fluid discharged fromthe regulation chamber A1 into the second suction chamber 43, and anorifice that is located in the high-pressure passage and regulates theflow rate of the discharged fluid flowing in the high-pressure passage.The pressure controller 75 controls the pressure of the regulationchamber A1 by controlling the valve. This allows the position of themovable body 71 to be adjusted.

The two coupling pieces 73 project toward the swash plate 50 from partof the annular open end of the movable body 71 as viewed in the axialdirection Z. More specifically, the two coupling pieces 73 projecttoward the swash plate 50 from a portion of the movable body 71 locatedtoward the side opposite to the distal portion of the lug arm 61 fromthe rotation shaft 20 as viewed in the axial direction Z. The twocoupling pieces 73 oppose each other in the pivot axes of the two pivotcenters M1 and M2 (direction in which pivot centers M1 and M2 extend).

The swash plate 50 includes a plate-shaped coupling receiving portion 76that projects from the second inclined surface 52 b and overlaps the twocoupling pieces 73 as viewed in the pivot axis. The coupling receivingportion 76 and the arm through hole 52 c are located in the secondinclined surface 52 b at opposite sides of the swash plate insertionhole 51. The coupling receiving portion 76 includes a coupling holethrough which a coupling pin 77 extending in the pivot axis can beinserted. The coupling pin 77 is located between the two coupling pieces73. The coupling pin 77 is inserted through the coupling hole and fixedto the two coupling pieces 73. Thus, the swash plate 50 is coupled tothe movable body 71. In this case, the movement of the movable body 71changes the inclination angle of the swash plate 50. That is, adjustmentof the position of the movable body 71 adjusts the inclination angle ofthe swash plate 50.

To simplify the drawings, the coupling pin 77 and the coupling hole havethe same shape. However, the coupling hole actually has an oval shapeelongated in the vertical direction and has a larger diameter than thecoupling pin 77 so as to correspond to changes in the inclination angleof the swash plate 50.

As shown in FIG. 1, the swash plate 50 includes a first projection 81that projects from the first inclined surface 52 a and a secondprojection 82 that projects from the second inclined surface 52 b. Thesecond projection 82 is separate from the coupling receiving portion 76.

The first projection 81 does not extend over the entire circumference ofthe first inclined surface 52 a. Rather, the first projection 81 extendsover a portion of the first inclined surface 52 a located at theopposite side of the arm through hole 52 c with respect to the swashplate insertion hole 51. The second projection 82 extends in thecircumferential direction around the swash plate insertion hole 51 inthe second inclined surface 52 b. The two projections 81 and 82 arelocated in the radial direction R at the inner side of a portion of theinclined surfaces 52 a and 52 b that is held by two shoes 121 and 122(described later). Thus, the swash plate 50 includes a circumferentialportion that is thinner than the portion where the two projections 81and 82 and the coupling receiving portion 76 are arranged.

A recovery spring 83 is fixed to the first shaft projection 20 a of therotation shaft 20. The recovery spring 83 extends in the axial directionZ from the first shaft projection 20 a toward the swash plate chamberA2. Further, an inclination reduction spring 84 is arranged between thepartition 72 and the swash plate 50. The inclination reduction spring 84includes one end fixed to the partition 72 and the other end fixed tothe swash plate 50. The inclination reduction spring 84 biases the swashplate 50 in a direction that decreases the inclination angle of theswash plate 50.

The compressor 10 includes pairs of cylinder bores 91 and 92. Thecylinder bores 91 and 92 of each pair are opposed to each other in theaxial direction Z and located at the outer side of the rotation shaft 20in the radial direction R in the housing 11. The cylinder bores 91 and92 are located at the outer side of the shaft holes 21 and 22 in theradial direction R. The pairs of the cylinder bores 91 and 92 extend inthe circumferential direction around the shaft holes 21 and 22 of thecylinder blocks 14 and 15. The cylinder bores 91 are opposed to thecylinder bores 92 at opposite sides of the swash plate chamber A2. Thecylinder bores 91 and 92 are coaxial.

To facilitate understanding, FIG. 1 shows only one of the cylinder bores91 and one of the cylinder bores 92. Further, the cylinder bores 91 and92 are separated from the suction passages 54 a and 54 b in thecircumferential direction so that the cylinder bores 91 and 92 do notinterfere with the suction passages 54 a and 54 b around the shaft holes21 and 22.

The cylinder bores 91 and 92 have the form of a tube (more specifically,cylindrical tube) and extend through the corresponding cylinder blocks14 and 15 in the axial direction Z. One opening of each of the cylinderbores 91 and 92 is in communication with the swash plate chamber A2, andthe other opening of each of the cylinder bores 91 and 92 is closed bythe valve/port body 23 or 24. The first valve/port body 23 partitionseach first cylinder bore 91 from the first suction chamber 33 and thefirst discharge chamber 34, and the second valve/port body 24 partitionseach second cylinder bore 92 from the second suction chamber 43 and thesecond discharge chamber 44.

As shown in FIG. 1, the valve/port bodies 23 and 24 close the openingsof the cylinder bores 91 and 92 and include suction ports 23 a and 24 athat are respectively in communication with the suction chambers 33 and43 and discharge ports 23 b and 24 b, which are respectively incommunication with the discharge chambers 34 and 44 through the valve.The suction ports 23 a and 24 a and the discharge ports 23 b and 24 bextend in the circumferential direction in correspondence with thecylinder bores 91 and 92 that extend in the circumferential direction.

As described above, refrigerant contains oil. Thus, oil exists in aspace where refrigerant exists, more specifically, in the swash plate A2and the cylinder bores 91 and 92 that are in communication with theswash plate A2.

The compressor 10 includes the double-headed piston 100 thatreciprocates in each pair of the cylinder bores 91 and 92 and the twoshoes 121 and 122 that couple the double-headed piston 100 to the swashplate 50.

The double-headed piston 100 is accommodated in each pair of thecylinder bores 91 and 92 so that the axial direction of thedouble-headed piston 100 corresponds to the axial direction Z of therotation shaft 20 (in other words, opposing direction of two cylinderbores 91 and 92). More specifically, the double-headed piston 100 isarranged in each pair of the cylinder bores 91 and 92 so that thedouble-headed piston 100 is coaxial with the two cylinder bores 91 and92.

The double-headed pistons 100 extend in the circumferential direction incorrespondence with the cylinder bores 91 and 92 extend in thecircumferential direction. That is, each pair of the cylinder bores 91and 92 includes one of the double-headed pistons 100.

The structures of the double-headed piston 100 and the like will now bedescribed in detail.

As shown in FIGS. 2 to 5, the double-headed piston 100 includes a neck101, shoe holders 102 and 112 that hold the two shoes 121 and 122, twoheads 103 and 113 located at the two ends in the axial direction of thedouble-headed piston 100, and two coupling portions 104 and 114 thatrespectively couple the shoe holders 102 and 112 to the heads 103 and113. The two shoe holders 102 and 112 oppose each other in the axialdirection of the double-headed piston 100. The neck 101 couples the twoshoe holders 102 and 112.

The coupling portions 104 and 114 include inner portions 105 and 115 andouter portions 106 and 116 extending in the axial direction of thedouble-headed piston 100. The inner portions 105 and 115 arerespectively opposed to the outer portions 106 and 116 in the radialdirection R. Further, the coupling portions 104 and 114 include plates107 and 117 that couple the inner portions 105 and 115 to the outerportions 106 and 116, respectively. The inner portions 105 and 115 arelocated at the inner side of the outer portions 106 and 116 in theradial direction R (i.e., in portion of double-headed piston 100 that isclose to rotation shaft 20).

The axial direction of the double-headed piston 100 is the direction inwhich the head 103 is opposed to the head 113, and the radial directionR is the direction in which the inner portions 105 and 115 are opposedto the outer portions 106 and 116. To facilitate understanding, adirection orthogonal to both of the axial direction of the double-headedpiston 100 and the opposing direction of the inner portions 105 and 115and the outer portions 106 and 116 is hereinafter referred to as thewidthwise direction W.

The coupling portions 104 and 114 of the present embodiment are deformedmore easily in the widthwise direction W than in the radial direction R.More specifically, the coupling portions 104 and 114 are configured tohave a smaller section modulus in the widthwise direction W than in theradial direction R. Each of the coupling portions 104 and 114 has awidth that is less than or equal to that of the neck 101.

As shown in FIG. 5, the two shoe holders 102 and 112 includesemi-spherical surfaces 102 a and 112 a. The semi-spherical surfaces 102a and 112 a are recessed away from each other. The circumferentialportion of the swash plate 50 is arranged between the shoe holders 102and 112.

The first shoe 121 of the two shoes 121 and 122 is located between thefirst inclined surface 52 a of the swash plate 50 and the firstsemi-spherical surface 102 a of the first shoe holder 102, and thesecond shoe 122 is located between the second inclined surface 52 b ofthe swash plate 50 and the second semi-spherical surface 112 a of thesecond shoe holder 112. The two shoes 121 and 122 are semi-spherical.The two shoes 121 and 122 include bottom surfaces that abut against thecircumferential portions of the corresponding inclined surfaces 52 a and52 b and spherical surfaces that abut against the correspondingsemi-spherical surfaces 102 a and 112 a. The shoe holders 102 and 112hold the two shoes 121 and 122 with the two shoes 121 and 122 holdingthe circumferential portions of the swash plate 50. Thus, the two shoes121 and 122 couple the double-headed piston 100 to the swash plate 50.

In such a structure, rotation of the swash plate 50 applies load,including a component in the axial direction Z, to the double-headedpiston 100 through the two shoes 121 and 122. This converts the rotationof the swash plate 50 into reciprocation of the double-headed piston100. In this case, the stroke of the double-headed piston 100 changes inaccordance with the inclination angle of the swash plate 50.

The neck 101 is located at an outer circumferential side of the swashplate 50, more specifically, at the outer side of the swash plate 50 inthe radial direction R. The neck 101 is larger in the widthwisedirection W than in the radial direction R so that the neck 101 isdeformable in the radial direction R. More specifically, the neck 101 isplate-shaped, and the radial direction R of the neck 101 refers to athickness-wise direction. The section modulus of the neck 101 is smallerin the radial direction R than in the widthwise direction W. The twoshoe holders 102 and 112 are located at the two ends of the innersurface of the neck 101 in the axial direction of the double-headedpiston 100.

In the present embodiment, the neck 101 has a width that is equal tothat of each of the shoe holders 102 and 112. However, the neck 101 mayhave a width that is greater than that of each of the shoe holders 102and 112.

As shown in FIG. 3, the outer surface of the neck 101 is curved inconformance with a wall surface 91 a that is the wall surface of thefirst cylinder bore 91. The outer surface of the neck 101 includes neckrecesses 101 a that are recessed from the outer surface of the neck 101toward the inner side in the radial direction R. The two neck recesses101 a are separated from each other in the widthwise direction W. Thus,the two ends of the neck 101 in the widthwise direction are thinner thanthe central portion of the neck 101 in the widthwise direction W andeasily deformed in the radial direction R.

As shown in FIGS. 2 to 5, each of the heads 103 and 113 is tubular andhas a bottom. The heads 103 and 113 include bottom surfaces 103 a and113 a, which have a slightly smaller diameter than the first wallsurfaces 91 a of the first cylinder bore 91 and a second wall surface 92a of the second cylinder bore 92 and side surfaces 103 b and 113 b(i.e., outer circumferential surfaces 103 b and 113 b), respectively.Further, the heads 103 and 113 open toward the shoe holders 102 and 112.

As shown in FIG. 5, the first wall surface 91 a of the first cylinderbore 91 is opposed to the side surface 103 b of the first head 103, anda first gap 108 is formed between the first wall surface 91 a and theside surface 103 b. The first head 103 is at least partiallyaccommodated in the first cylinder bore 91 regardless of where thedouble-headed piston 100 is located.

The first cylinder bore 91 includes a first compression chambers A4 thatis defined by the bottom surface 103 a of the first head 103, the firstwall surfaces 91 a, and the first valve/port body 23. The firstcompression chamber A4 is in communication with the first suctionchamber 33 with the first suction ports 23 a located in between and isin communication with the first discharge chamber 34 with the firstdischarge port 23 b located in between.

In the same manner, the second wall surface 92 a of the second cylinderbore 92 is opposed to the side surface 113 b of the second head 113, anda second gap 118 is formed between the second wall surface 92 a and theside surface 113 b. The second head 113 is at least partiallyaccommodated in the second cylinder bore 92 regardless of where thedouble-headed piston 100 is located.

The second cylinder bore 92 includes a second compression chambers A5that is defined by the bottom surface 113 a of the second head 113, thesecond wall surfaces 92 a, and the second valve/port body 24. The secondcompression chamber A5 is in communication with the second suctionchamber 43 with the second suction ports 24 a located in between and isin communication with the second discharge chamber 44 with the seconddischarge port 24 b located in between.

In such a structure, reciprocation of the double-headed piston 100 drawsfluid from the suction chambers 33 and 43 into the compression chambersA4 and A5, where the fluid is compressed. Then, the fluid is dischargedinto the discharge chambers 34 and 44. The stroke of the double-headedpiston 100 changes in accordance with the inclination angle of the swashplate 50 and varies the displacement of the compressed fluid. That is,the compressor 10 of the present embodiment is of a variabledisplacement type.

As shown in FIG. 6, the position of the double-headed piston 100 wherethe inclination angle is the maximum and the first compression chamberA4 is most compressed (i.e., position where double-headed piston 100 ismost proximate to first valve/port body 23) is referred to as the firstposition (top dead center of first head 103 of double-headed piston100). Further, as shown in FIG. 7, the position of the double-headedpiston 100 where the inclination angle is the maximum and the secondcompression chamber A5 is most compressed (i.e., position wheredouble-headed piston 100 is most proximate to second valve/port body 24)is referred to as the second position (top dead center of second head113 of double-headed piston 100). The double-headed piston 100reciprocates between the first position and the second position. Thatis, the double-headed piston 100 can reciprocate from the first positionto the second position.

As shown in FIG. 5, the head 103 has a larger diameter than the secondhead 113. The first cylinder bore 91 is larger than the second cylinderbore 92 in correspondence with the difference in diameter of the twoheads 103 and 113. More specifically, the first wall surface 91 a has alarger diameter than the second wall surface 92 a. Thus, the two gaps108 and 118 have substantially the same size (more specifically, samelength in radial direction R).

The wall surfaces 91 a and 92 a of the two cylinder bores 91 and 92,which are coaxially opposed to each other have different diameters.Thus, the outer portion of the first wall surface 91 a in the radialdirection R is located outward in the radial direction R from the outerside of the second wall surface 92 a in the radial direction R. As shownin FIG. 6, the outer portion of the first wall surface 91 a in theradial direction R is flush with a side wall inner surface 15 a that isan inner surface of the side wall of the second cylinder block 15 thatdefines the swash plate chamber A2. The side wall inner surface 15 a andthe second wall surface 92 a form a step.

As shown in FIGS. 3 and 5, the first outer portion 106 extends in theaxial direction of the double-headed piston 100 from the outer portionof the first head 103 in the radial direction R and couples the firsthead 103 to the first shoe holder 102 with the neck 101. Morespecifically, the first outer portion 106 connects the end of the neck101 where the first shoe holder 102 is arranged to the outer portion ofthe first head 103 in the radial direction R. The first outer portion106 is a plate having a width in the widthwise direction W and athickness in the radial direction R. The first outer portion 106includes an outer surface curved in conformance with the first wallsurface 91 a.

The first outer portion 106 has a width that is less than or equal tothat of the neck 101. Further, the first outer portion 106 is at leastpartially narrower than the two shoe holders 102 and 112. In the presentembodiment, the portion of the first outer portion 106 excluding thelongitudinal ends of the first outer portion 106 is narrower than thetwo shoe holders 102 and 112.

The first inner portion 105 extends in the axial direction of thedouble-headed piston 100 from the inner portion of the first head 103 inthe radial direction R. The first inner portion 105 includes a firstbasal portion 105 a located near the first head 103 and a first distalportion 105 b located near the first shoe holder 102. The first distalportion 105 b of the first inner portion 105 is located between thefirst head 103 and the first shoe holder 102 as viewed in the radialdirection R, more specifically, located at the portion of the firstcoupling portion 104 closer to the first shoe holder 102 than the firsthead 103. The first distal portion 105 b corresponds to “an end of theinner portion near the shoe holder.”

As shown in FIG. 4, the first inner portion 105 is a plate having awidth in the widthwise direction W and a thickness in the radialdirection R. The first inner portion 105 includes a first fixed-widthportion 105 c having a fixed width. The first fixed-width portion 105 cis located between the two ends 105 a and 105 b. In the presentembodiment, the first fixed-width portion 105 c has a width that is lessthan that of each of the two shoe holders 102 and 112. The first distalportion 105 b of the first inner portion 105 is wider than the firstfixed-width portion 105 c.

As shown in FIG. 5, the first inner portion 105 is located furtherinward from the side surface 103 b of the first head 103. Thus, thefirst distal portion 105 b of the first inner portion 105 is locatedfurther inward from the side surface 103 b of the first head 103.

The first inner portion 105 includes a first inner surface 105 dopposing the first wall surface 91 a in the radial direction R. Thefirst inner surface 105 d is curved in conformance with the first wallsurface 91 a. The first inner surface 105 d is farther from the portionof the first wall surface 91 a opposing the first inner surface 105 dthan the side surface 103 b of the first head 103. That is, the sidesurface 103 b of the first head 103 and the first inner surface 105 dform a step so that the first inner surface 105 d is farther from thefirst wall surface 91 a than the side surface 103 b of the first head103.

The step may include, for example, a surface orthogonal to the axialdirection of the double-headed piston 100 as shown in FIG. 5. Instead,the step may be, for example, tapered so that the outer diametergradually decreases from the first head 103 toward the first shoe holder102.

The step between the side surface 103 b of the first head 103 and thefirst inner surface 105 d may have any dimension, for example, less thanor equal to 1 mm (excluding 0 mm). In each of the drawings, tofacilitate understanding, the step is larger than the actual one.Further, the first distal portion 105 b has an edge that is obliquelycut. Thus, the edge of the first inner surface 105 d near the firstdistal portion 105 b is inclined.

The first inner portion 105 is located at the inner side of the firstshoe holder 102 in the radial direction R. Thus, the first distalportion 105 b of the first inner portion 105 and the first shoe holder102 form a step as viewed in the widthwise direction W.

The first coupling portion 104 includes a first rib 109 that connectsthe first shoe holder 102 and the first distal portion 105 b of thefirst inner portion 105, which form a step. The first rib 109 connectsthe first distal portion 105 b of the first inner portion 105 to thefirst shoe holder 102 so that a first space A11 is defined by the sideof the first distal portion 105 b of the first inner portion 105 asviewed in the widthwise direction W. More specifically, the first rib109 is inclined as viewed in the widthwise direction W. As shown in FIG.4, the length X11 of the first inner portion 105 in the axial directionof the double-headed piston 100 is greater than the length X12 of thefirst rib 109.

As shown in FIGS. 2 to 5, the thickness-wise direction of the firstplate 107 in the first coupling portion 104 is the widthwise directionW. That is, the first plate 107 has a thickness in the widthwisedirection W. The thickness of the first plate 107 is smaller than thewidths of the first inner portion 105 and the first outer portion 106.The first plate 107 includes a first through hole 107 a extending in thewidthwise direction W. The first through hole 107 a is, for example,defined by a wall recessed toward the first shoe holder 102 as viewed inthe widthwise direction W and is in communication with the interior ofthe first head 103, which is tubular and has a bottom.

The second coupling portion 114 is basically the same as the firstcoupling portion 104 except that, for example, the second couplingportion 114 in the axial direction of the double-headed piston 100 islonger than the first coupling portion 104.

More specifically, as shown in FIGS. 3 and 5, the second outer portion116 extends in the axial direction of the double-headed piston 100 fromthe outer portion of the second head 113 in the radial direction R andcouples the second head 113 to the second shoe holder 112 with the neck101. The second outer portion 116 includes an outer surface curved inconformance with the second wall surface 92 a.

As shown in FIGS. 2 to 5, the second inner portion 115 extends in theaxial direction of the double-headed piston 100 from the inner portionof the second head 113 in the radial direction R. The second innerportion 115 includes a second basal portion 115 a located near thesecond head 113 and a second distal portion 115 b located near thesecond shoe holder 112. The second distal portion 115 b is locatedbetween the second head 113 and the second shoe holder 112 as viewed inthe radial direction R, more specifically, located at the part of thesecond coupling portion 114 closer to the second shoe holder 112 thanthe second head 103. The second distal portion 115 b corresponds to “anend of the inner portion near the shoe holder.”

As shown in FIG. 4, the second inner portion 115 is a plate having awidth in the widthwise direction W and a thickness in the radialdirection R. The second inner portion 115 includes a second fixed-widthportion 115 c having a fixed width. The second fixed-width portion 115 cis located between the two ends 115 a and 115 b. In the presentembodiment, the second fixed-width portion 115 c has a width that isless than that of each of the two shoe holders 102 and 112. The seconddistal portion 115 b of the second inner portion 115 is wider than thefixed-width portion 115 c.

The second inner portion 115 is located further inward from the sidesurface 113 b of the second head 113. The second inner portion 115includes a second inner surface 115 d opposing the second wall surface92 a in the radial direction R. The second inner surface 115 d is curvedin conformance with the second wall surface 92 a. The second innersurface 115 d is farther from the portion of the second wall surface 92a opposing the second inner surface 115 d than the side surface 113 b ofthe second head 113. That is, the side surface 113 b of the second head113 and the second inner surface 115 d form a step so that the secondinner surface 115 d is farther from the second wall surface 92 a thanthe side surface 113 b of the second head 103. The step between the sidesurface 113 b of the second head 113 and the second inner surface 115 dmay have any dimension, for example, less than or equal to 1 mm(excluding 0 mm). In each of the figures, to facilitate understanding,the dimension of the step is larger than the actual one. Further, thesecond distal portion 115 b has an edge that is obliquely cut. Thus, theedge of the second inner surface 115 d near the second distal portion115 b is inclined.

As shown in FIG. 5, the second inner portion 115 is located at the innerside of the second shoe holder 112 in the radial direction R. Thus, thesecond distal portion 115 b of the second inner portion 115 and thesecond shoe holder 112 form a step. The second coupling portion 114includes a second rib 119 that connects the second shoe holder 112 andthe second distal portion 115 b of the second inner portion 115, whichform a step. The second rib 119 connects the second distal portion 115 bof the second inner portion 115 to the second shoe holder 112 so that asecond space A12 is defined by the side of the second distal portion 115b of the second inner portion 115 as viewed in the widthwise directionW. More specifically, the second rib 119 is inclined as viewed in thewidthwise direction W. As shown in FIG. 4, the length X21 of the secondinner portion 115 in the axial direction of the double-headed piston 100is greater than the length X22 of the second rib 119.

As shown in FIGS. 2 to 5, the thickness of the second plate 117 of thesecond coupling portion 114 is smaller than the widths of the secondinner portion 115 and the second outer portion 116. The second plate 117includes a second through hole 117 a extending in the widthwisedirection W. The second through hole 117 a is, for example, defined by awall recessed toward the second shoe holder 112 as viewed in thewidthwise direction W and is in communication with the interior of thesecond head 113, which is tubular and has a bottom.

As shown in FIGS. 3 to 5, the outer surface of the neck recesses 101 aincludes a rotation stopper 123 that restricts rotation of thedouble-headed piston 100 in the two cylinder bores 91 and 92. Therotation stopper 123 is located closer to the second shoe holder 112than the neck recesses 101 a, more specifically, on the end of the outersurface of the neck 101 that is closer to the second shoe holder 112. Inother words, the rotation stopper 123 may be located on the outersurface of the neck 101 closer to the second head 113 than the firsthead 103 or on the outer surface of the neck 101 at a location that iscloser to the second coupling portion 114 than the first couplingportion 104. The rotation stopper 123 extends in the widthwise directionW. As shown in FIG. 4, the two ends of the rotation stopper 123 in thewidthwise direction W extend out of the neck 101 as viewed in the radialdirection R. The rotation stopper 123 includes an outer surface curvedin conformance with the side wall inner surface 15 a. The outer surfaceof the rotation stopper 123 abuts against the side wall inner surface 15a to restrict rotation of the double-headed piston 100 in the cylinderbores 91 and 92.

In the present embodiment, the rotation stopper 123 is arranged near thesecond shoe holder 112 and not near the first shoe holder 102. Thus, theportion of the neck 101 near the first shoe holder 102 is deformed moreeasily than the portion near the second shoe holder 112, and the portionof the neck 101 near the second shoe holder 112 has a higher strengththan the portion of the neck 101 near the first shoe holder 102.

Further, the double-headed piston 100 is movable to where the rotationstopper 123 abuts against the open end of the first cylinder bore 91that is closer to the swash plate chamber A2. That is, the portion ofthe neck 101 near the first shoe holder 102 of the double-headed piston100 can be partially inserted into the first cylinder bore 91.

Fluid in the compression chambers A4 and A5 and the swash plate appliesload to the double-headed piston 100. Load includes force applied fromthe swash plate 50 through the two shoes 121 and 122 and compressionreaction force that results from the compression of fluid in thecompression chambers A4 and A5. The force includes a component in theaxial direction Z and a component that acts toward the inner side in theradial direction R. That is, the double-headed piston 100 receivesbending load that acts toward the inner side in the radial direction R.

Further, the degree of load applied to the double-headed piston 100varies depending on, for example, the inclination angle of the swashplate 50, the position of the double-headed piston 100 during a singlereciprocation, and the pressure of the compression chambers A4 and A5.That is, in accordance with the operation situation of the compressor10, a low load may be applied to the double-headed piston 100(hereinafter referred to as “low-load period”), and a high load that ishigher than the low load may be applied to the double-headed piston 100(hereinafter referred to as “high-load period”).

During the low-load period, the double-headed piston 100 receives loadthat is less than a specific threshold value. The low-load period maysatisfy, for example, at least one of the following two conditions: (A)the inclination angle of the swash plate 50 is equal to the minimuminclination angle or closer to the minimum inclination angle than themaximum inclination angle; and (B) the compression reaction force thatthe double-headed piston receives from the compression chambers A4 andA5 is less than a threshold value.

During the high-load period, the double-headed piston 100 receives loadthat is greater than the specific threshold value. The high-load periodmay satisfy, for example, at least one of the following two conditions:(A) the inclination angle of the swash plate 50 is equal to the maximuminclination angle or closer to the maximum inclination angle than theminimum inclination angle; and (B) the compression reaction force thatthe double-headed piston receives from the compression chambers A4 andA5 is greater than or equal to a threshold value.

However, the low-load period and the high-load period do not have to beset in accordance with the above conditions. Instead, the low-loadperiod and the high-load period may be set in accordance with, forexample, the operation condition of the compressor 10. The high-loadperiod may be, for example, when the compressor 10 is activated or whenthe vehicle is accelerated at a rate that is greater than or equal to apredetermined threshold acceleration rate. The low-load period may bewhen the compressor 10 is operated as the vehicle is traveling at aconstant speed or as the vehicle is accelerated at a rate that is lessthan the predetermined threshold acceleration rate.

Alternatively, the low-load period and the high-load period may be setin accordance with the operation condition of a vehicle air-conditioner.For example, during the high-load period, the vehicle air-conditionermay be activated or a passenger compartment temperature may bemaintained. As another option, during the high-load period, the vehicleair-conditioner may be operated to reach a set target temperature underthe condition that the difference of the set target temperature and thepassenger compartment temperature is greater than or equal to athreshold value, and during the low-load period, the vehicleair-conditioner may be operated to reach the set target temperatureunder the condition that the difference of the set target temperatureand the passenger compartment temperature is less than a thresholdvalue.

The low load may be referred to as a first load, and the high load maybe referred to as a second load.

The double-headed piston 100 during the low-load period will now bedescribed.

Referring to FIG. 5, the double-headed piston 100 receives a relativelysmall bending load during the low-load period. Thus, the neck 101resists deforming. In this case, the side surfaces 103 b and 113 b ofthe heads 103 and 113 slide along (i.e., abut against) the wall surfaces91 a and 92 a of the cylinder bores 91 and 92 and thus receive bendingload. In this case, the distal portions 105 b and 115 b of the Innerportions 105 and 115 are farther from the wall surfaces 91 a and 92 a ofthe cylinder bores 91 and 92 than the side surfaces 103 b and 113 b ofthe heads 103 and 113. Thus, the double-headed piston 100 reciprocateswith the distal portions 105 b and 115 b separated from the wallsurfaces 91 a and 92 a of the cylinder bores 91 and 92. The low-loadperiod may be when the neck 101 is not deformed or when the neck 101 isdeformed but the distal portions 105 b and 115 b do not abut against thewall surfaces 91 a and 92 a of the cylinder bores 91 and 92.

The double-headed piston 100 during the high-load period will now bedescribed. In the present embodiment, the double-headed piston 100 islocated at the first position or the second position during thehigh-load period.

As shown in FIG. 6, when the double-headed piston 100 is located at thefirst position, the first distal portion 105 b of the first innerportion 105 is opposed to the first wall surface 91 a in the radialdirection R. Further, when the double-headed piston 100 is located atthe first position, the double-headed piston 100 receives a relativelylarge bending load. In this case, the neck 101 is deformed toward theinner side in the radial direction R so that the entire double-headedpiston 100 is bent and bulged toward the inner side in the radialdirection R.

When the double-headed piston 100 is bent, the side surfaces 103 b and113 b of the heads 103 and 113 slide along (i.e., abut against) the wallsurfaces 91 a and 92 a, and the first distal portion 105 b (morespecifically, portion of first inner surface 105 d that corresponds tofirst distal portion 105 b) slides along the first wall surface 91 a.That is, the side surfaces 103 b and 113 b of the heads 103 and 113 andthe first distal portion 105 b receive bending load. In this case, sincethe distance from the first distal portion 105 b to the first shoeholder 102 in the axial direction of the double-headed piston 100 isshorter than the distance from the first head 103 to the first shoeholder 102, bending moment that is produced at the double-headed piston100 is reduced as compared to when bending load is received only by theheads 103 and 113. The first distal portion 105 b corresponds to a “loadreceiving portion.”

The high-load period is when the neck 101 receives bending load anddeforms such that the distal portions 105 b and 115 b abut against thewall surfaces 91 a and 92 a of the cylinder bores 91 and 92. That is,the specific threshold value refers to a lower limit value of load inwhich the distal portions 105 b and 115 b abut against the wall surfaces91 a and 92 a of the cylinder bores 91 and 92 when the neck 101 isdeformed.

When the first distal portion 105 b abuts against the first wall surface91 a, further deformation of the double-headed piston 100 is restricted.In addition, when the double-headed piston 100 is bent, priority isgiven to the sliding of the edge of the first distal portion 105 b,which is obliquely inclined, along the first wall surface 91 a. When thefirst distal portion 105 b slides along the first wall surface 91 a, thefirst fixed-width portion 105 c is separated from the first wall surface91 a.

Further, a first oil collection region A21 is defined between the sidesurface 103 b of the first head 103 and the first distal portion 105 b.The first oil collection region A21 is located between the first wallsurface 91 a and the first fixed-width portion 105 c. Oil suspended inrefrigerant flows into the first oil collection region A21. Then, theoil is supplied to where the side surface 103 b of the first head 103slides along (i.e., abuts against) the wall surface 91 a and to wherethe first distal portion 105 b slides along the first wall surface 91 a.

When the double-headed piston 100 is located at the first position, thesecond projection 82 of the swash plate 50 is located in the secondspace A12. This avoids interference between the double-headed piston 100and the second projection 82. The second space A12 does not interferewith the coupling receiving portion 76 and the second projection 82regardless of the inclination angle of the swash plate 50 and theposition of the double-headed piston 100 in the cylinder bores 91 and92.

As shown in FIG. 7, when the double-headed piston 100 is located at thesecond position, the second distal portion 115 b of the second innerportion 115 is opposed to the second wall surface 92 a in the radialdirection R. Further, since the double-headed piston 100 receives arelatively large bending load, the neck 101 is deformed toward the innerside in the radial direction R so that the entire double-headed piston100 is bent and bulged toward the inner side in the radial direction R.The side surface 103 b of the head 103 slides along the first wallsurfaces 91 a, and the side surface 113 b of the second head 113 and thesecond distal portion 115 b (more specifically, portion of second innersurface 115 d that corresponds to second distal portion 115 b) slidealong the second wall surface 92 a. That is, the side surfaces 103 b and113 b of the heads 103 and 113 and the second distal portion 115 breceive bending load. In this case, the distance from the second distalportion 115 b to the second shoe holder 112 in the axial direction ofthe double-headed piston 100 is shorter than the distance from thesecond head 113 to the second shoe holder 112. This reduces the bendingmoment produced at the double-headed piston 100 as compared to when thebending load is received only by the heads 103 and 113. The seconddistal portion 115 b corresponds to the “load receiving portion.”

When the second distal portion 115 b abuts against the second wallsurface 92 a, further deformation of the double-headed piston 100 isrestricted. In addition, when the double-headed piston 100 is bent,priority is given to the sliding of the edge of the second distalportion 115 b, which is obliquely inclined, along the second wallsurface 92 a. The second fixed-width portion 115 c is separated from thesecond wall surface 92 a.

Further, a second oil collection region A22 is defined between the sidesurface 113 b of the second head 113 and the second distal portion 115b. The second oil collection region A22 is located between the secondwall surface 92 a and the second fixed-width portion 115 c. Oilsuspended in refrigerant flows into the second oil collection regionA22. Then, the oil is supplied to where the side surface 113 b of thesecond head 113 slides along the second wall surface 92 a and to wherethe second distal portion 115 b slides along the second wall surface 92a.

When the double-headed piston 100 is located at the second position, thefirst projection 81 of the swash plate 50 is located in the first spaceA11. This avoids interference between the double-headed piston 100 andthe first projection 81. The first space A11 does not interfere with thedouble-headed piston 100 and the first projection 81 regardless of theinclination angle of the swash plate 50 and the position of thedouble-headed piston 100 in the cylinder bores 91 and 92.

The above embodiment has the advantages described below.

(1) The compressor 10 is of a double-headed piston type swash plate typethat compresses fluid in the compression chambers A4 and A5 of thecylinder bores 91 and 92 when rotation of the swash plate 50 rotates thedouble-headed piston 100 in the two cylinder bores 91 and 92.

The double-headed piston 100 includes the two shoe holders 102 and 112,which hold the two shoes 121 and 122 and are opposed to each other inthe axial direction of the double-headed piston 100, and the neck 101,which couples the two shoe holders 102 and 112 and is located at acircumferential side of the swash plate 50. The neck 101 is deformablein the radial direction R. The double-headed piston 100 includes the twoheads 103 and 113, which are respectively arranged at the two ends ofthe double-headed piston 100 in the axial direction, and the twocoupling portions 104 and 114, which respectively couple the two heads103 and 113 to the two shoe holders 102 and 112.

In such a structure, when the double-headed piston 100 receives load,the neck 101 is deformed toward the inner side in the radial direction Rso that the double-headed piston 100 is bent and bulged toward the innerside in the radial direction R. The coupling portions 104 and 114include the distal portions 105 b and 115 b, which serve as the loadreceiving portions receiving bending load that is applied from the swashplate 50 to the double-headed piston 100 and acts toward the inner sidein the radial direction R. The distal portions 105 b and 115 b arelocated between the heads 103 and 113 and the shoe holders 102 and 112as viewed in the radial direction R. During the low-load period, theload applied to the double-headed piston 100 is less than the specificthreshold value. In this case, the distal portions 105 b and 115 b areseparated from the wall surfaces 91 a and 92 a of the cylinder bores 91and 92. During the high-load period, the load applied to thedouble-headed piston 100 is greater than the specific threshold value.In this case, when the neck 101 is deformed, each of the distal portions105 b and 115 b abuts against the corresponding wall surface (firstdistal portion 105 b abuts against first wall surface 91 a and seconddistal portion 115 b abuts against second wall surface 92 a) andreceives bending load.

In such a structure, during the low-load period, the side surfaces 103 band 113 b of the heads 103 and 113 abut against the wall surfaces 91 aand 92 a of the cylinder bores 91 and 92, and the distal portions 105 band 115 b do not abut against the wall surfaces 91 a and 92 a. Thislimits the power loss of the double-headed piston 100 that may occurwhen the distal portions 105 b and 115 b abut against the wall surfaces91 a and 92 a.

During the high-load period, one of the two distal portions 105 b and115 b receives bending load. Thus, three portions, namely, one of thetwo distal portions 105 b and 115 b and the side surfaces 103 b and 113b of the heads 103 and 113, receive bending load. In this case, sincethe distance from the distal portions 105 b and 115 b to the shoeholders 102 and 112 to which bending load is applied is shorter in theaxial direction of the double-headed piston 100 than the distance fromthe heads 103 and 113 to the shoe holders 102 and 112. This reduces thebending moment and thus reduces stress that is applied to thedouble-headed piston 100. Accordingly, the strength that countersbending load of the double-headed piston 100 is increased. Further, thedouble-headed piston 100 receives the bending load over more portionsduring the high-load period than during the low-load period. Thisdisperses the bending load and thus limits local wear.

(2) The distal portions 105 b and 115 b of the inner portions 105 and115 are located closer to the shoe holders 102 and 112 than the heads103 and 113. This shortens the distance from each of the portions thatreceive bending load (i.e., distal portions 105 b and 115 b serving asload receiving portions) to each of the portions where bending load isapplied (i.e., shoe holders 102 and 112). Thus, bending moment isreduced in a further preferred manner, and the strength that countersbending load is further increased.

(3) The coupling portions 104 and 114 respectively include the outerportions 106 and 116, which extend in the axial direction of thedouble-headed piston 100, and the inner portions 105 and 115, which arelocated at the inner sides of the outer portions 106 and 116 in theradial direction R and extended from the heads 103 and 113 in the axialdirection of the double-headed piston 100. The inner portions 105 and115 are opposed to the outer portions 106 and 116 in the radialdirection R. The inner portions 105 and 115 respectively include theinner surfaces 105 d and 115, which are opposed in the radial directionR to the wall surfaces 91 a and 92 a of the cylinder bores 91 and 92.The inner surfaces 105 d and 115 d and the side surfaces 103 b and 113 bof the heads 103 and 113 form a step so that the inner surfaces 105 dand 115 d are located further inward (i.e., farther from wall surfaces91 a and 92 a of cylinder bores 91 and 92) than the side surfaces 103 band 113 b. The distal portions 105 b and 115 b, which are the ends ofthe inner portions 105 and 115 located near the shoe holders 102 and112, serve as the load receiving portions that receive bending loadduring the high-load period. In such a structure, since the innersurfaces 105 d and 115 d and the side surfaces 103 b and 113 b of theheads 103 and 113 form a step, the distal portions 105 b and 115 b areseparated from the wall surfaces 91 a and 92 a of the cylinder bores 91and 92 during the low-load period in which the neck 101 is not deformed.When the neck 101 is deformed such that the double-headed piston 100 isbent and bulged toward the inner side in the radial direction R, one ofthe distal portions 105 b and 115 b abuts against the wall surface ofthe corresponding cylinder bore and receives bending load. Thus,advantage (1) is obtained in a relatively simple structure.

In particular, the inner portions 105 and 115 extend from the heads 103and 113 in the axial direction of the double-headed piston 100, and thedistal portions 105 b and 115 b of the inner portions 105 and 115 areparts of the inner portions 105 and 115 located closest to the shoeholders 102 and 112. When the distal portions 105 b and 115 b receivebending load, the distance from each of the portions that receivebending load to each of the portions where bending load is applied isfurther shortened. This reduces bending moment.

(4) The inner portions 105 and 115 respectively include the fixed-widthportions 105 c and 115 c, each having a fixed width. The distal portions105 b and 115 b are wider than the fixed-width portions 105 c and 115 c.This increases the areas of the portions that receive bending load andthus reduces wear of the distal portions 105 b and 115 b (morespecifically, portions of inner surfaces 105 d and 115 d that formdistal portions 105 b and 115 b). Further, the fixed-width portions 105c and 115 c that do not abut against the wall surfaces 91 a and 92 a ofthe cylinder bores 91 and 92 are narrow. This reduces the weight of thedouble-headed piston 100.

(5) The coupling portions 104 and 114 respectively include the ribs 109and 119 that connect the distal portions 105 b and 115 b and the shoeholders 102 and 112 so that the spaces A1 and A12 are defined beside thedistal portions 105 b and 115 b as viewed in the widthwise direction W.This allows the swash plate 50 to pass the spaces A11 and A12. Thus,interference between the swash plate 50 and the double-headed piston 100is avoided.

(6) The lengths X11 and X21 of the inner portions 105 and 115 are largerthan the lengths X12 and X22 of the ribs 109 and 119 in the axialdirection of the double-headed piston 100. In such a structure, thedistal portions 105 b and 115 b of the inner portions 105 and 115 becomeclose to the shoe holders 102 and 112 to avoid interference with theswash plate 50. This avoids interference with the swash plate 50 andincreases the strength that counters bending load of the double-headedpiston 100 in the radial direction R.

(7) The cylinder bores 91 and 92 include oil. During the high-loadperiod, the oil enters the oil collection regions A21 and A22 definedbetween the distal portions 105 b and 115 b, which abut against the wallsurfaces 91 a and 92 a of the cylinder bores 91 and 92, and the heads103 and 113. The oil that flow into the oil collection regions A21 andA22 is supplied to where the distal portions 105 b and 115 b abutagainst the wall surfaces 91 a and 92 a and to where the side surfaces103 b and 113 b of the heads 103 and 113 abut against the wall surfaces91 a and 92 a. Thus, the abut portions are supplied with a sufficientamount of oil, and wear is reduced.

(8) The double-headed piston 100 reciprocates from the first position tothe second position when the inclination angle of the swash plate 50 isthe maximum. The first distal portion 105 b is opposed to the first wallsurface 91 a when the double-headed piston 100 is located at the firstposition. The second distal portion 115 b is opposed to the second wallsurface 92 a when the double-headed piston 100 is located at the secondposition. In such a structure, when the double-headed piston 100 islocated at least at the first location or the second location, thedistal portions 105 b and 115 b receive bending load. This avoidssituations in which the distal portions 105 b and 115 b are unable toreceive bending load when receiving a relatively high load.

(9) The compressor 10 includes the actuator 70 that changes theinclination angle of the swash plate 50. The actuator 70 includes themovable body 71, which is movable in the axial direction Z of therotation shaft 20, and the partition 72, which defines the controlchamber A3 in cooperation with the movable body 71. The compressor 10changes the inclination angle of the swash plate 50 when the movablebody 71 moves in accordance with the pressure of the control chamber A3.Thus, adjustment of the pressure of the control chamber A3 allows forvariable displacement.

When variable displacement is performed, the controllability of thevariable displacement needs to be increased. In the present embodiment,the coupling portions 104 and 114 are relatively narrow (for example,less than or equal to width of neck 101) so that the coupling portions104 and 114 are easily deformed in the widthwise direction W. Thus, ascompared to the piston that is wide in the widthwise direction W toreceive side force, the weight of the double-headed piston 100 isreduced. This increases the controllability of variable displacement.

(10) The second head 113 has a smaller diameter than the first head 103.In such a structure, the first head 103 and the second head 113respectively include refrigerant pressure receiving areas that differfrom each other. Accordingly, the first head 103 and the second head 113have different compression reaction forces that result from thecompression of fluid. This allows variable displacement to be performedrelatively easily. Thus, the controllability of variable displacement isincreased.

(11) The neck recesses 101 include the rotation stopper 123 thatrestricts rotation of the double-headed piston 100 in the two cylinderbores 91 and 92. The rotation stopper 123 is located at the portion ofthe neck 101 that is closer to the second head 113 than the first head103. In such a structure, the rotation stopper 123 is located at thesmall diameter side where the strength has a tendency of being lowerthan the large diameter side. This limits decreases in the strength ofthe second head 113, which is an undesirable situation that may occurwhen the heads 103 and 113 have different diameters.

It should be apparent to those skilled in the art that the presentinvention may be embodied in many other specific forms without departingfrom the spirit or scope of the invention. Particularly, it should beunderstood that the present invention may be embodied in the followingforms.

The coupling portions 104 and 114 are not limited to any specific shape.For example, each of the coupling portions may be smaller than the heads103 and 113 and have a tubular or cylindrical shape.

The load receiving portions that receive bending load do not have to bethe distal portions 105 b and 115 b. Instead, the load receivingportions may be, for example, projections that project from the innersurfaces 105 d and 115 d. In this case, the inner surfaces 105 d and 115d may be located sufficiently outward from the side surfaces 103 b and113 b of the heads 103 and 113 in the radial direction R so that theprojections do not slide along the wall surfaces 91 a and 92 a of thecylinder bores 91 and 92 during the low load. Alternatively, thedimensions and the like of the projections may be adjusted.

Further, the load receiving portions may be the fixed-width portions 105c and 115 c. In this case, the fixed-width portions 105 c and 115 cproject further inward in the radial direction R (i.e., toward portionsof wall surfaces 91 a and 92 a opposing fixed-width portions 105 c and115 c) from the distal portions 105 b and 115 b. In the same manner, theload receiving portions may be the basal portions 105 a and 115 a of theinner portions 105 and 115. That is, the load receiving portions may belocated at the portions of the coupling portions 104 and 114 closer tothe heads 103 and 113 than the shoe holders 102 and 112 (between shoeholders 102 and 112 and heads 103 and 113). However, it is preferredthat the load receiving portions be the distal portions 105 b and 115 bin order to further reduce bending moment.

The inner portions 105 and 115 may be omitted. In this case, forexample, protrusions may protrude from the middle portions of the outerportions 106 and 116 toward the inner side in the radial direction R,and the protrusions may include distal portions that are separated fromthe wall surfaces 91 a and 92 a of the cylinder bores 91 and 92. In sucha structure, when the neck 101 is deformed, the distal portions of theprotrusions abut against the wall surfaces 91 a and 92 a. In otherwords, the load receiving portions may have any specific shape as longas the coupling portions 104 and 114 located between the heads 103 and113 and the shoe holders 102 and 112 include the load receivingportions.

The two fixed-width portions 105 c and 115 c may be omitted. Forexample, the inner portions 105 and 115 may be gradually narrowed orwidened from the basal portions 105 a and 115 a toward the distalportions 105 b and 115 b. In this case, the distal portions 105 b and115 b may be wider than the portions of the inner portions 105 and 115excluding the distal portions 105 b and 115 b. Alternatively, the distalportions 105 b and 115 b may be narrower than the shoe holders 102 and112. As another option, one of the two fixed-width portions 105 c and115 c may be omitted.

The fixed-width portions 105 c and 115 c may be wider than the shoeholders 102 and 112. In other words, the inner portions 105 and 115 maybe at least partially narrower than the shoe holders 102 and 112, andthe entire inner portions 105 and 115 may be wider than the shoe holders102 and 112. Alternatively, the inner positions 105 and 115 may be widerthan the neck 101.

Each of the coupling portions 104 and 114 may have a width that is lessthan or equal to that of the neck 101. Alternatively, each of thecoupling portions 104 and 114 may have a width that is greater than thatof the neck 101.

The outer portions 106 and 116 may be thicker or thinner than the innerportions 105 and 115. Further, at least one of the two outer portions106 and 116 may be omitted.

In the embodiment, the first coupling portion 104 in the axial directionof the double-headed piston 100 is longer than the second couplingportion 114. Instead, the two coupling portions 104 and 114 may have thesame length. Alternatively, the second coupling portion 114 may belonger than the first coupling portion 104.

The first head 103 and the second head 113 may have the same size.Alternatively, the second head 113 may be larger than the first head103. In addition, the heads 103 and 113 may be cylindrical.

The ribs 109 and 119 may have any specific structure as long as the ribs109 and 119 do not interfere with the swash plate 50. For example, theribs 109 and 119 may be L-shaped or reverse L-shaped as viewed in thewidthwise direction W.

The neck 101 and the coupling portions 104 and 114 are not limited tothe forms illustrated in the embodiment.

The neck recess 101 a may have any shape. Further, the neck recess 101 amay be omitted.

The through holes 107 a and 117 a are not limited to any specific shape.Further, at least one of the through holes 107 a and 117 a may beomitted, and at least one of the plates 107 and 117 may be omitted.

The rotation stopper 123 may be located closer to the first shoe holder102 than the neck recesses 101 a. Alternatively, the rotation stopper123 may be located closer to both of the first shoe holder 102 and thesecond shoe holder 112 than the neck recesses 101 a. Further, therotation stopper 123 may be omitted.

The actuator 70 may have any specific structure as long as the actuator70 is capable of changing the inclination angle of the swash plate 50.In the same manner, the link mechanism 60 may have any specificstructure as long as the link mechanism 60 is capable of transmittingpower from the rotation shaft 20 to the swash plate 50.

At least one of the first projection 81 and the second projection 82 maybe omitted.

The number of cylinder bores 91 and 92 and the number of double-headedpistons 100 are not limited to those of the embodiment and may each be,for example, one.

The lengths X11 and X21 of the inner portions 105 and 115 may be lessthan or equal to the lengths X12 and X22 of the ribs 109 and 119.

At least one of each of the inner portions 105 and 115 and each of theouter portions 106 and 116 may be slightly inclined with respect to theaxial direction of the double-headed piston 100.

The compressor 10 of the embodiment is of a variable displacement type.Instead, the compressor 10 may be of a fixed displacement type in whichthe inclination angle of the swash plate 50 is fixed.

The fluid that is subject to compression by the compressor 10 is notlimited to refrigerant and may be, for example, air.

The compressor 10 does not have to be installed in a vehicle.

The above embodiment may be combined with each of the modified examples.

Therefore, the present examples and embodiments are to be considered asillustrative and not restrictive and the invention is not to be limitedto the details given herein, but may be modified within the scope andequivalence of the appended claims.

1. A double-headed piston type swash plate compressor comprising: arotation shaft extending in an axial direction and a radial direction; ahousing that accommodates the rotation shaft; a swash plate that rotateswhen the rotation shaft rotates; two cylinder bores located in thehousing at an outer side of the rotation shaft in the radial direction;a double-headed piston that reciprocates in the two cylinder bores; andtwo shoes that couple the double-headed piston to the swash plate,wherein the two cylinder bores and the double-headed piston define twocompression chambers, rotation of the swash plate reciprocates thedouble-headed piston in the two cylinder bores and compresses fluid ineach of the compression chambers, the double-headed piston includes: twoshoe holders that hold the two shoes, wherein the two shoe holders areopposed to each other in an axial direction of the double-headed piston;a neck that couples the two shoe holders, wherein the neck is located atan outer circumferential side of the swash plate and deformable in theradial direction; two heads respectively located at two ends of thedouble-headed piston in the axial direction of the double-headed piston,wherein each of the two heads includes a side surface opposing a wallsurface of the cylinder bore; and two coupling portions that couple thetwo shoe holders and the two heads, respectively, at least one of thetwo coupling portions includes a load receiving portion located betweenthe corresponding head and the corresponding shoe holder as viewed inthe radial direction, wherein the load receiving portion is configuredto receive bending load that is applied from the swash plate to thedouble-headed piston and acts toward an inner side in the radialdirection, the load receiving portion is separated from the wall surfaceof the cylinder bore when load applied to the double-headed piston isless than a specific threshold value, and the load receiving portionabuts against the inner wall of the cylinder bore and receives thebending load when the load applied to the double-headed piston isgreater than the specific threshold value.
 2. The double-headed pistontype swash plate compressor according to claim 1, wherein each of thetwo coupling portions includes: an outer portion extending in the axialdirection of the double-headed piston; and an inner portion located atthe inner side of the outer portion in the radial direction and extendedfrom the head in the axial direction of the double-headed piston, theinner portion includes an inner surface opposing the wall surface of thecylinder bore in the radial direction, the inner surface and the sidesurface of the head form a step so that the inner surface is fartherfrom the wall surface of the cylinder bore than the side surface of thehead, and the load receiving portion is an end of the inner portion nearthe corresponding shoe holder.
 3. The double-headed piston type swashplate compressor according to claim 2, when referring to a directionorthogonal to both of the axial direction and an opposing direction ofthe inner portion and the outer portion as a widthwise direction, theinner portion includes a fixed-width portion having a fixed width, andthe end of the inner portion near the corresponding shoe holder is widerthan the fixed-width portion.
 4. The double-headed piston type swashplate compressor according to claim 1, wherein the cylinder boreincludes oil and an oil collection region located between the loadreceiving portion and the corresponding head; and the oil enters the oilcollection region when load applied to the double-headed piston isgreater than the threshold value.
 5. The double-headed piston type swashplate compressor according to claim 1, each of the two coupling portionsincludes the load receiving portion, when the double-headed pistonreciprocates from a first position to a second position, a first one ofthe load receiving portions that is included in a first one of the twocoupling portions opposes the wall surface of the cylinder bore when thedouble-headed piston is located at the first position, and a second oneof the load receiving portions that is included in a second one of thetwo coupling portions opposes the wall surface of the cylinder bore whenthe double-headed piston is located at the second position.
 6. Thedouble-headed piston type swash plate compressor according to claim 1,further comprising an actuator that changes an inclination angle of theswash plate, wherein the actuator includes: a movable body that ismovable in the axial direction of the rotation shaft; and a partitionthat defines a control chamber in cooperation with the movable body, andthe actuator is operable to change an inclination angle of the swashplate when the movable body is moved in accordance with pressure of thecontrol chamber.
 7. The double-headed piston type swash plate compressoraccording to claim 6, wherein the two heads include a first head and asecond head, and the second head has a smaller diameter than a diameterof the first head.